Fibrous composition



Patented Apr. 2, 1935 1 996 UNITED STATES PATENT OFFICE rmaous co'urosmon corded s. Wlghtman, Upper Montolalr, n. s.

No Drawing. Original application December 18,

1928, Serial No. 820,911. Divided and this application March 20, 1931, Serial No. 524,207. In Canada December 5, 1929 '1 Claim. (Cl. 154-2.)

This invention relates to fibrous compositions tained can be handled in the same manner as any including a bonding agent, and more specifically other fibrous material, and laid into paper or relates to such compositions supplied in sheet sheet form on a paper making machine after form and intended for the manufacture of lamibeating to efiect a partial hydration of the fibers.

5 nated products for insulating and kindred pur- Following the usual procedure, the sheet after 5 poses. Bonding agents in prevalent use for such drying is coated or impregnated with a potencompositions are the resinoids, or compounds of tially reactive resinoid in solution and the solvent a resinous character which can be changed from removed. Any of the known resinoids, for exama fusible, soluble and potentially reactive state ple the phenol-formaldehyde condensation prodl0 to a substantially infuslble and insoluble state ucts, or compositions described in a Patent by the application of .heat, since compositions 1,677,417 to Turkington granted July 17, 1928 including such bonding agents impart superior comprising phenol-fatty-oil methylene reaction electrical and mechanical properties to articles products, can be used for this purpose. The made therefrom. The bonding agents are cusresinoids of the Turkington disclosure are tough l5 tomarily applied to sheets of the fibrous material and elastic when cold and form flexible laml- I as solutions to form coatings or impregnations, nated products with sheets of high alpha celand laminated products are made therefrom by lulose content, from which insulating parts can superposing a number of coated sheets and simulbe stamped out. taneously applying heat and pressure to convert A typical sample of laminatedmaterial stock. v

the resinoid binder to the insoluble, infusible conprepared from superposed sheets of paper with 20 dition; but they can be otherwise incorporated an alpha cellulose fiber content of 94 per cent or with the fibers, for example by the wet process as more bonded with a coating or impregnating described in a P n o B k land 1,1 62 composition consisting of a solution of a resinoid granted November 16, 1915. made from cresol and formaldehyde and added As fibrous material for such compositions, wood in amount so as to yield a stock with about 40 per 25 pulp is commercially in demand on account of cent resinoid content, and molded under heat at I its low cost; but, as heretofore supplied, it has a temperature of about 170 C. and pressure at 3 not been found desirable, particularly in comabout 1000 pounds per square inch to convert the positions of sheet form for laminated products resinoid to the substantially infusible state, had

for electrical insulation, on account of the exa water absorption over a period of 24 hours of 30 cessive rate of water absorption and/or other about 1.3 per cent; a. trait wood fiber paper stock Pr p r i being such as to render the laminated as used heretofore and similarly prepared showed products formed therefrom less unsatisfactory for an absorption of 3.5 per cent. In addition it this and other purposes, particularly those remay be here noted that alpha cellulose pulp as qulring highest quality. is more readily prepared in paper form than C n ry to this past experience with wood kraft pulp and the beating time required for P p, I have disc ver d the ompositions can be kraft is from one-third to two-thirds longer made from wood fibers, yielding products having than that required for alpha-cellulose. In a rate of water absorption so low as to compare comparative t t; ith ott n fiber sto k,

40 favorably in this respect with other fibrous inalpha cellulose stock had a higher Helmsulating materials, such as cotton, and to be mc Strength 920 volts per nf alpha 11mm otherwise made more suitable for electrical inm 840 om mil 10 mm, sulatlon, provided the wood pulp be treated so v r as to be relatively high in resistant cellulose fibers, ggi g: g fz fg fifi that is, provided approximately 90 and prefer- 45 quency while the cotton fiber stock measured ably 94 per cent or more of the pulp content is M t 3 5 In M I m mes of tensile alpha cellulose. Such a pulp can be prepared for u mec c D De it mm example by treating or cooking a sulfite pulp, and transverse st'engthelastic obtained by digesting wood chips in an acid sulfite alpha cellulose and laminated pieces tested solution, with an alkaline liquor, such as caustic were about the same order, 8411,! cellulose 50 soda, best followed by bleaching with chlorine or m a Somewhat 511991101 menlth t0 other suitable agent; other methods or modificathe ethersror & strength of over 17, 0 pound! to tions thereof known to the paper making art can the q fl inch, and les! bflmeneee than the be employed. kraft, its modulus of elasticity as measured 56 The wood ,pulp rich in alpha cellulose so ob about 1,1 ,000. 56 I ized by a dielectric strength greater than 850 volts per mil, power factor less than 3.4, tensile strength greater than 17,000 pounds per square inch and water absorption less than 3 per cent in 24 hours.

GORDON E. WIGH'I'MAN. 

